Isoflavones are a unique class of phytoestrogens—plant hormones—that naturally occur in many plants, including soybeans (Glycine max). The three isoflavones found in soybeans are genistin, daidzin, and glycitin, typically in a ratio of genistin: daidzin: glycitin of 1.1:1.0:0.3.
It is widely anticipated that market demand for soy isoflavones will continue to grow. Scientists have demonstrated that isoflavones have the ability to inhibit cancer cell growth, and some researchers believe that isoflavones may contribute to soy's ability to lower blood-cholesterol levels.
Research shows that soy isoflavones have a wide range of health benefits that include moderating normal symptoms associated with menopause and promoting bone and heart health. It appears that about 100 milligrams of isoflavones (expressed in the glycoside form) are necessary to deliver most of these health benefits. This is about the average amount consumed daily by Asians, who have a much lower incidence of heart disease, osteoporosis, and uncomfortable menopausal symptoms compared to Western societies.
Some women's health problems during and after middle age are related to a changing hormonal state. Consuming soy isoflavones can help moderate the natural hormonal changes associated with several menopausal and postmenopausal symptoms.
Soy isoflavones are potent anti-oxidants capable of reducing the amount of LDL-cholesterol (bad cholesterol) that undergoes modification in the body. Entry of the modified LDL-cholesterol into the walls of blood vessels contributes to the formation of plaques. These plaques cause the blood vessels to lose their ability to function normally. Research in both animals and humans shows that ingesting soy isoflavones can help maintain normal blood vessel function
Soy isoflavones are actively studied for their effects on maintaining and improving bone health. Women can lose up to 15% of their total bone mass in the early years following the onset of menopause. This loss can be quite detrimental, particularly to women who enter menopause with weaker bones. Emerging research shows that isoflavones appear to play a role in both preventing bone loss and increasing bone density.
A body of research suggests that the most pharmacologically active soy isoflavone is genistin. Therefore, a method of separating genistin from daidzin and glycitin or of enriching the proportion of genistin in soy isoflavone concentrates is desirable.
The isoflavones found in soybeans occur predominantly as glucones or glycosides (with sugars), with only a minor aglucones or aglycons (without sugars) content. The glucones have the glucose molecule attached, and include genistin, daidzin and glycitin. The aglucones are isoflavones without the glucose molecule, and they include genistein, daidzein and glycitein. In addition, an appreciable percentage of the glucones occur as malonates or acetates. The malonyl and acetyl moieties of soy isoflavones glucones are thermally labile, particularly at elevated pH (from about 9.5 to 11.0) and can be easily converted to the corresponding simple glucones by digestion at moderate temperatures with sodium or potassium hydroxide.
Traditionally, the separation of genistin from daidzin and glycitin has required laborious ultrafiltration followed by preparative chromatography (see, e.g., U.S. Pat. No. 5,679,806) or ion-exchange resins (see, e.g., U.S. Pat. No. 6,020,471) of large volumes of solutions due to the modest solubility of soy isoflavones. These processes employ various resins to adsorb the isoflavones from aqueous solutions heated to various temperatures to take advantage of the temperature-sensitive differential solubilities of isoflavones in order to effect their separation (see, e.g., U.S. Pat. No. 5,702,752).